Activities in complex networks are often both too important to ignore and too tedious to watch. We created a network monitoring system, Peep, that replaces visual monitoring with a sonic `ecology' of natural sounds, where each kind of sound represents a specific kind of network event. This system combines network state information from multiple data sources, by mixing audio signals into a single audio stream in real time. Using Peep, one can easily detect common network problems such as high load, excessive traffic, and email spam, by comparing sounds being played with those of a normally functioning network. This allows the system administrator to concentrate on more important things while monitoring the network via peripheral hearing.